An internal combustion engine makes an air-fuel mixture of air and fuel burn in a cylinder. In control of an internal combustion engine, it is known to estimate the amount of air which flows into the cylinder and use the amount of air which flows into the cylinder and the target air-fuel ratio as the basis to determine the amount of fuel which is fed into the cylinder. The amount of air which flows into the cylinder, for example, can be estimated based on the output value of an air flow detector which is arranged in the engine intake passage.
Further, the method is known of using numerical calculations using a model calculation formula derived from a model of the system arranged in the engine intake passage so as to estimate the amount of air which flows into a cylinder. For example, a system is known of preparing in advance a model calculation formula of a throttle valve, intake pipe, etc. and using values of various parameters of the internal combustion engine and the model calculation formula to estimate the amount of air which is filled into the cylinder.
Japanese Patent Publication (A) No. 2007-231840 discloses a control system which is provided with an air flowmeter which is provided in an engine intake passage, a throttle model which estimates an air flow amount passing through a throttle, and an air flowmeter model which uses an estimated value of the air flow amount passing through the throttle calculated by the throttle model as the basis to calculate an anticipated output value of the air flowmeter using a air flowmeter model calculation formula, which system uses an actual measured value of the air flowmeter and the anticipated output value to control the internal combustion engine.
Further, a system is known which estimates the air flow amount passing through a throttle valve from the output values of various types of sensors and maps.
Japanese Patent Publication (A) No. 2006-9745 discloses a method of correction of an air flow sensor output which finds a deviation between an intake air amount which is predicted based on an engine speed and an accelerator opening degree and the intake air amount which is detected by the air flow sensor when cutting the recirculation of the exhaust gas and makes corrections in a direction making the output of the air flow sensor increase when this deviation exceeds a preset threshold value.